BitBuilderEvery part explains itself
Each gate, latch, flip-flop and display comes with a plain-English explanation of what it does and where you’d use it.
UNDERSTAND WHAT’S UNDER THE HOOD
Design. Simulate. Learn.
Bit by bit.
Build digital circuits from the ground up — from a single logic gate to the components of a computer — and watch every signal move as it happens.
Try it free in your browser
Also on the App Store for iPad and Mac, and Google Play for Android.
A LITTLE LOGIC,
LIVETRY IT YOURSELF ↘
| A | B | OUT |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
AND gate. A: 1. B: 0. Output: 0.
START WITH THE FUNDAMENTALS
From one gate
to a computer.
Build your understanding, one layer at a time.
-
01
Gates
AND, OR, NOT, NAND, NOR, XOR, XNOR.
-
02
Latches & flip-flops
SR, D, JK and T: circuits that remember.
-
03
Registers & memory
Clock a value into a register, then store thousands of words in RAM and ROM.
-
04
Buses
Wires up to 64 bits wide, with splitters, mergers and width adapters.
-
05
Displays & I/O
LEDs, seven-segment displays, colour pixels, a speaker, clocks, buttons and DIP switches.
Every step is something you build yourself.
BUILT TO TEACH
It explains itself.
BitBuilder doesn’t just run your circuit. It tells you what it’s doing, and why.
A truth table for anything
Select a gate, or a chip you built from gates, and see every combination of inputs and the output it gives.
Diagnostics that point
A loop that never settles, or two outputs fighting over one wire: BitBuilder says what’s wrong in plain words and shows you where.
Open up any chip
A chip you built isn’t a black box. Switch it to run live, look inside, and watch the circuit you wired do its work.
01 — SIMULATE
It’s live.
Flip a switch and watch the signal spread through your circuit in real time. No compile button, no waiting.
- Lay out as many boards as you like on one canvas.
- Drag parts onto a board, or tap to place them. Search finds any part, including your own chips.
- Wires route themselves. They can animate their flow, and a bus can show its value in hex or decimal.
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02 — ABSTRACT
Make your
own chips.
Build a circuit, turn it into a chip, then drop it into bigger circuits as a single part. A half adder becomes a full adder becomes an ALU — the same way real hardware is designed.
Edit the original and every copy updates.
HALF ADDER→FULL ADDER→ALU
- Start from scratch, or turn a board you’ve already wired into a chip.
- Name its pins and make any of them up to 64 bits wide.
- Design its face with shapes, text and freehand drawing.
- Add a Display Port and put its own inputs and outputs on its face, from colour pixels to a speaker.
- Chips run as fast lookup tables. Switch one to run live and look inside it while it runs.
- Keep a chip in My Chips for every document, or inside just one file. Share it as a file, tests included.
Free includes 3 custom chips. Pro removes the limit.
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03 — DEBUG PRO
Find out why.
Stop the circuit the moment something happens, then step it forward one component at a time.
- Pause when a pin rises, falls or changes, when an output hits a value, or every time a part recomputes.
- Skip the first few hits and stop on the one you care about.
- Every wire freezes showing its value, and a banner says what stopped it.
- Trace back through what caused each change.
- Turn every breakpoint off at once without losing any. They work inside a chip while you build it, too.
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04 — VERIFY PRO
Prove it works.
Test benches run your chip against the inputs and outputs you expect, so you know it’s right rather than hoping.
- Write a table of expected results, or lay out every input combination in one tap.
- For chips that remember, write a script: set inputs, advance the clock, check what came out. Replay to any step to watch it.
- Expect exact values, “anything”, or “not this”, in binary, decimal or hex.
- Edit the circuit and its tests are flagged for a re-run.
- When a chip fails because a chip inside it fails, BitBuilder points you to the real culprit.
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05 — EVERYWHERE
Your bench, on every screen.
BitBuilder runs on iPad, Mac, Android and the web.
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everywhere-android.png2560 × 1600
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IPADMACANDROIDWEB
06 — THE PARTS BIN
The whole parts bin.
Over 30 parts, all free. Anything missing, you build yourself and save as a chip.
INPUTS6
- Toggle
- Button
- Clock
- DIP switches
- High
- Low
LOGIC GATES7
- AND
- OR
- NOT
- NAND
- NOR
- XOR
- XNOR
LATCHES & FLIP-FLOPS8
- SR latch
- D latch
- JK latch
- T latch
- SR flip-flop
- D flip-flop
- JK flip-flop
- T flip-flop
MEMORY3
- Register
- RAM
- ROM
BUSES3
- Splitter
- Merger
- Adapter
OUTPUTS5
- LED
- 7-segment
- Decoder
- Pixel
- Speaker
YOUR OWN3
- Your chips
- Text notes
- Images
More of the workbench
Clocks you can set to any rate
ROM loaded from any binary file
Seven-segment & colour pixel displays
A speaker that plays any 8-bit pitch
Notes & images on the canvas
Copy, paste & duplicate across boards
Export as PNG or PDF
Share whole documents & single chips
Keyboard shortcuts on iPad & Mac
Step a signal through one part at a time
Your own defaults for boards & wires
Light & dark themes
MORE ROOM TO BUILD
Everything’s free to learn.
Go Pro to go further.
THE FOUNDATIONS
Free
- Every part and the full simulator
- Look inside any running chip
- Truth tables, diagnostics and guided tours
- Up to 3 custom chips
- Export and share your work
- No account needed
THE FULL WORKBENCH
BitBuilder Pro
A$12.99ONCE
- Unlimited custom chips
- Test benches: tables and scripts
- Breakpoints and stepping
- Causality tracing
- Everything in Free
One-time purchase. No subscription.
Buy once, unlocked everywhere — iPad, Mac, Android and web.
Price in Australian dollars. The App Store and Google Play show the equivalent in your currency.
A FEW MORE BITS
Good questions.
Do I need to know electronics?
No. BitBuilder starts at a single logic gate. If you can follow “on” and “off”, you can start.
Which platforms is it on?
iPad, Mac, Android and the web. The web version runs in your browser, with nothing to install.
Is it a subscription?
No. BitBuilder is free, and Pro is a one-time purchase of A$12.99.
If I buy Pro on one device, do I have to buy it again?
No. Sign in with your BitBuilder account and Pro unlocks on every platform.
Do I need an account?
No. The free tier never needs one. An account exists for one reason: so BitBuilder Pro follows you to your other devices. Sign in with Apple, Google or email.
Is it good for courses like nand2tetris?
Yes. You build the same ladder, from NAND gates through adders and an ALU to registers, RAM and ROM, as reusable chips, then check each one with a test bench the way the course does.
Can I share my circuits and chips?
Yes. Share a whole document, or share a single chip as a file that someone else can import into their own library. A chip’s test bench travels with it.
Can I export a picture of my circuit?
Yes. Export any board as a PNG or a PDF, ready for notes, slides or an assignment.
What happens to my work if I sign out?
Nothing. Your circuits and chips stay exactly where they are. Signing out only changes whether Pro is unlocked on that device.
WL
I built BitBuilder because the moment I understood how a few logic gates become a computer, everything clicked — and I wanted a tool that makes that moment easy to reach.
No ads, no subscriptions. Just a really good workbench.